The present invention relates to ophthalmic filter materials, in particular, to lenses designed to protect the eye from the effects of strong sunlight.
The present invention relates to ophthalmic filter materials, particularly, to ophthalmic filter lenses. These materials selectively transmit radiation in the visual and near-visual regions of the electromagnetic radiation spectrum. The materials of the present invention are primarily concerned with controlled transmission of sunlight and ambient light through ophthalmic lenses.
The present invention was developed employing photochromic lenses, particularly, photochromic lenses made of organic polymers. The present invention may find application in products other than ophthalmic lenses, such as visors and shields or windows.
Certain diseases of the eye and/or visual deficiencies may be caused by, or may be aggravated by, strong sunlight. The radiation at the short end of the visible spectrum, that is, at wavelengths on the order of 400-550 nanometers (nm), seems to create the greatest problems for some patients. The eye contains two different kinds of photo receptors, viz., cones and rods. The cones comprise the principal receptors in daylight vision (diurnal vision or photopic vision), and the rods constitute the principal receptors in night vision (nocturnal vision or scotopic vision). The cones are located generally in the center portion of the retina, and are much greater in number per unit area. They permit the recognition of fine detail, presumably because they function largely independently of one another. The cones also permit color vision, i.e., they allow hues and saturation to be distinguished. In the presence of bright light, the eye is most sensitive to radiation at about 555 nm. In general, the rods are located at the peripheral portions of the retina, there being few, if any, rods found in the central retina. The rods do not permit the recognition of colors, only shades of gray. The peak wavelength sensitivity is near 505 nm.
Most of the ophthalmic filter lenses of the past have been made on the basis of inorganic glass photochromic lenses. These photochromic glasses contain, in addition to an inorganic glass phase, a precipitated microcrystalline silver halide phase. It is the silver halide phase that is considered to cause the reversible darkening of the glass under exposure to light.
Past ophthalmic filter lenses have been made from polycarbonate optical plastics with a tintable coating thereon. However, such plastic lenses were not photochromic. Thus they cannot fit the needs of some of the patients who suffer from strong sunlight. For persons subject to aphakia, retinitis (including photoretinitis, retinitis caused by virus, fungi or bacteria infection, contusion, and degenerative retinopathy), and retinitis pigmentosa, photochromic filter lenses are desired. It has generally been accepted that retinal degeneration can be decelerated by preventing both receptors of the retina (cones and rods) from being subject to bright illumination and great changes in light levels. Photochromic lenses would act to compensate for differences in indoor and outdoor radiation intensity levels.
There remains a genuine need for ophthalmic filter lenses based on photochromic plastic lenses. While desired to have the wavelength filtration properties of the prior art glass-based photochromic ophthalmic filter lenses discussed above, such plastic lenses should be advantageously durable and lighter in weight. Light transmission properties of the lenses should be able to impart sufficiently low color distortion. It would be beneficial for the lenses to have good photochromic properties in terms of colorability, darkening and fading kinetics, and durability in coloration, etc.
Thus the present invention provides a photochromic plastic filter lens having a polymer matrix with at least one photochromic agent distributed therein, applied thereto or associated therewith and at least one ophthalmic filtering dye applied thereto, associated therewith or distributed therein, which provides filtering properties having a dominant wavelength between 570 and 605 nm and a color purity between 50% and 75%. The present inventive lenses are particularly useful for users with eye conditions described above. They operate to modify the stimuli to the photoreceptors of the retina in a manner beneficial to the patient.
In another aspect of the present invention, for patients suffering from retinitis pigmentosa, the present invention provides a plastic photochromic filter lens having a polymer matrix with at least one photochromic agent distributed therein, applied thereto or associated therewith and at least one ophthalmic filtering dye applied thereto, associated therewith or distributed therein, which exhibits substantially reduced transmittance of radiation having wavelengths shorter than about 550 nm, a photopic transmittance no greater than about 25% in the faded state and no greater than about 5% in the darkened state, and a scotopic transmittance no greater than about 3% in the faded state and no greater than about 1% in the darkened state, at a wavelength between about 450-550 nm.
Preferably, the polymer matrix of the ophthalmic lens of the present invention is made of polymers selected from the group consisting of poly(C1-C12 alkyl methacrylates), poly(oxyalkylene dimethacrylates), poly(alkoxylated phenol methacrylates), cellulose acetate, cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate, poly(vinyl acetate), poly(vinyl alcohol), poly(vinyl chloride), poly(vinylidene chloride), thermoplastic polycarbonates, polyesters, polyurethanes, poly(ethylene terephthalate), polystyrene, poly(xcex1-methylstyrene), poly(styrene-co-methyl methacrylate), poly(styrene-co-acrylonitrile), polyvinylbutyral and polymers and/or copolymers of monomers selected from the group consisting of polyol (allyl carbonate) monomers, polyfunctional acrylate monomers, polyfunctional methacrylate monomers, diethylene glycol dimethacrylate monomers, diisopropenyl benzene monomers, ethoxylated bisphenol A dimethacrylate monomers, ethylene glycol bismethacrylate monomers, poly(ethylene glycol) bismethacrylate monomers, ethoxylated phenol methacrylate monomers, alkoxylated polyhydric alcohol acrylated monomers and diallylidene pentaerythritol monomers.
Preferably, the at least one photochromic agent is selected from the group consisting of spiroxazines, spiropyrans and chromenes. Preferably, the photochromic agent is distributed throughout the polymer matrix.
In another aspect of the present invention, it is provided a method to produce the ophthalmic photochromic plastic lenses of the present invention, which comprises treating a photochromic plastic article in at least one solution of at least one filtering dye for a time sufficient to impart the recited characteristics to the article.
In still another aspect, the present invention provides a method for producing the ophthalmic photochromic filter lenses of the present invention, which comprises adding and dispersing an effective amount of at least one photochromic agent and an effective amount of at least one ophthalmic filtering agent to a monomer or a mixture of monomers, and thereafter polymerizing the resultant mixture into a photochromic filtering polymer to produce the lens.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from the description or recognized by practicing the invention as described in the written description and claims hererof, as well as the appended drawings.
It is to be understood that the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework to understanding the nature and character of the invention as it is claimed.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s) of the invention, and together with the description serve to explain the principles and operation of the invention.